I might incorporate around a few pint or so of distilled h2o.. anymore and I might pick up some coolant to mix. if it goes off yet again, convey it on the dealer. its probably just evap lack of the h2o portion of the coolant blend. glycol doesnt evap as https://felixghrhh.mdkblog.com/32918546/types-of-coolant-for-bmw-335i-can-be-fun-for-anyone